1. Field
The present disclosure relates to an electronic parking brake actuator, and more particularly, to an electronic parking brake actuator including a planetary gear set.
2. Background
An electronic parking brake (EPB) is an apparatus electronically control the driving of a parking brake. The EPB is installed on a general disc brake and performs a parking brake function. To operate the EPB, an additional actuator is necessary. The actuator of the EPB includes a motor installed inside a housing and a gear assembly for transferring power and reducing speed is disposed on an output shaft of the motor.
The gear assembly may include a planetary gear set for changing speed. The planetary gear set may include a sun gear coupled with a shaft, a plurality of planetary gears engaged with a circumference of the sun gear, and a ring gear engaged with the planetary gear. The ring gear is fixed inside the housing. In general, a coupling rib is formed to protrude from an outer circumferential surface of the ring gear, a slot is formed inside the housing, and the coupling rib is inserted into the slot, thereby mounting the ring gear on the housing.
Considering a state of the ring gear which continuously receives torque and a tolerance with respect to the slot of the housing which is injection-molded, a gap may occur between the coupling rib and the slot in a configuration in which the coupling rib slides on the slot. When a gap occurs between the ring gear and the housing, the performance and durability of a product may have serious defects.